Showing papers on "Electric discharge published in 2002"

Discharge lamp lighting circuit

Abstract: A discharge lamp lighting circuit facilitates carrying out re-ignition and addresses a problem than can arise due to an influence of a capacitor in an auxiliary lighting circuit. A driving voltage generating portion supplies an AC driving voltage to a discharge lamp to be a driving target. An auxiliary lighting circuit is provided on a terminal side of the discharge lamp. An auxiliary lighting capacitor, an auxiliary lighting resistor and a switch are provided in series between the terminal of the discharge lamp and a fixed voltage terminal. A control circuit controls a conducting state of the switch. The switch is brought into an ON state before the discharge lamp is turned ON, and is brought into an OFF state after the discharge lamp is turned ON.

Effect of a DC corona electrical discharge on the airflow along a flat plate

Abstract: Ability of a DC electrical discharge to control low-velocity airflow along a flat plate is analyzed. Specifically, the electrodes are flush mounted on the insulating surface of the plate creating a tangential corona discharge at close vicinity of the wall. In this paper, visualizations of the low-velocity airflow (up to 1.4 m/s corresponding to Re=16 000) along the flat plate are presented. They show that the ionic wind induced by the corona discharge modifies the original airflow considerably, resulting in the airflow reattachment to the wall and reduction of the wake size. Velocity measurements by particle imaging velocimetry and by Pitot tube are conducted in a wind-tunnel loop for higher airflow velocities (up to 11 m/s corresponding to Re=117 800). Results show that the corona discharge at such high airflow velocities does affect significantly the velocity profile within the viscous boundary layer.

Decomposition of Organic Compounds in Water by Direct Contact of Gas Corona Discharge: Influence of Discharge Conditions

Abstract: Water purification experiments to decompose phenol, acetic acid, and Rhodamine B in water were conducted using a direct contact of gas corona discharge to the water surface. It was shown that O2 was important in the gas phase for the degradation process, and the negative corona showed higher degradation rates than the positive corona. It was found that the organic contaminants can effectively be decomposed by the present method without pH adjustment. The experimental results indicated that there were optimized values in the O2 concentration, the gas resident time above the water, and the cathode−anode gap. It was also indicated that the O2/CO2 mixture showed a higher degradation rate than the O2/N2 mixture for the gas phase. As the degradation mechanism, the uncharged short-lived radicals are considered to be important.

Effect of Electrical Discharge on Separation Processes and Shocks Position in Supersonic Airflow.

Abstract: The paper analyses and discusses the results of resent experimental works on influence of non-uniform plasma formation on characteristics of near-wall layers and separated areas in high-speed airflow. Fresh experimental results are being presented, which are obtained at condition of small-scale model duct. Two different aerodynamic situations are investigated: surface electrical discharge in a free stream and surface discharge in separated zone behind the wall step. The discharge properties and structure are studied as well as the change of the gasdynamic structure of the flow due to electric discharge excitation. Images of the shocks interaction with the plasma overlayer observed by the Schlieren method are shown. The effect of the flow instability damping by the plasma layer is demonstrated. Application of the surface type of electric discharge for the flow modification in ducts, inlets and combustors is discussed. The work has been fulfilled in frames of Advance Flow/Flight Control (AFFC) concept.

Reduction of Bacillus Subtilis and Aspergillus Niger spores using nonthermal atmospheric gas discharges

Abstract: Nonthermal gas discharges at atmospheric pressure, such as dielectric barrier discharges are currently investigated for low-temperature packaging sterilization in order to reach the conditions required for aseptic food packaging. In particular, understanding the basic sterilization mechanisms and the enhancement of the main bacterial reduction pathways are the goals of our investigations. For this purpose, germ reduction experiments were carried out with Bacillus Subtilis and Aspergillus Niger spores using different gas mixtures and plasma conditions with the direct and the indirect influence of barrier discharges. In order to analyze the contribution of UV radiation during plasma germ deactivation, experiments with different excimer UV lamps, also driven by barrier discharges in special UV-emitting gas mixtures, have been carried out. Results of germ reduction experiments using barrier discharges and prospects for atmospheric discharge systems, suitable for industrial packaging sterilization, are presented in this paper.

Electric-arc-induced gratings in non-hydrogenated fibres: fabrication and high-temperature characterizations

Abstract: Long-period fibre gratings are written in non-hydrogenated standard single-mode fibres, using electric discharge. We have obtained a transmitted spectrum with low insertion loss (<0.2 dB) and resonance peak isolation of -24 dB at 1545 nm. The model, based on coupled mode theory, predicts reasonably well the peak positions and isolations. We have performed very high temperature characterizations of the realized gratings, in the range 30-1200 °C. We have shown a specific spectral shift of the resonance peaks with temperature. We report a modal dependence of wavelength shift with temperature. Temperature annealing of the gratings, at 200, 400 and 600 °C show high thermal stability compared with CO2 and UV-induced ones, but annealing at 800 and 900 °C exhibit an irreversible spectral shift. The temperature sensitivity values are in good agreement with recently published works. These characterizations will help us to understand the writing mechanism of the grating by an electric discharge in standard single-mode fibres.

Pulsed high voltage electric discharge disinfection of microbially contaminated liquids

Abstract: Aims: To examine the use of a novel multielectrode slipping surface discharge (SSD) treatment system, capable of pulsed plasma discharge directly in water, in killing micro-organisms. Methods and Results: Potable water containing Escherichia coli and somatic coliphages was treated with pulsed electric discharges generated by the SSD. The SSD system was highly efficient in the microbial disinfection of water with a low energy utilization (η ≈ 10 –4 kW h l –1 ). Conclusions: The SSD treatment was effective in the destruction of E. coli and its coliphages through the generation of u.v. radiation, ozone and free radicals. Significance and Impact of the Study: The non-thermal treatment method can be used for the eradication of micro-organisms in a range of contaminated liquids, including milk, negating the use of pasteurization. The method utilizes multipoint electric discharges capable of treating large volumes of liquid under static and flowing regimes.

Application of infrared spectroscopy to monitoring gas insulated high-voltage equipment: electrode material-dependent SF6 decomposition

Abstract: Sulfur hexafluoride is a chemically inert gas which is used in gas insulated substations (GIS) and other high-voltage equipment, leading to a significant enhancement of apparatus lifetime and reductions in installation size and maintenance requirements compared to conventional air insulated substations. However, component failures due to aging of the gas through electrical discharges may occur, and on-site monitoring for risk assessment is needed. Infrared spectroscopy was used for the analysis of gaseous by-products generated from electrical discharges in sulfur hexafluoride gas. An infrared monitoring system was developed using a micro-cell coupled to an FTIR spectrometer by silver halide fibers. Partial least-squares calibration was applied by using a limited number of optimally selected spectral variables. Emphasis was placed on the determination of main decomposition products, such as SOF2, SOF4, and SO2F2. Besides the different electrical conditions, the material of the plane counter electrode of the discharge chamber was also varied between silver, aluminum, copper, tungsten, or tungsten/copper alloy. For the spark experiments the point electrode was the same material as chosen for the plane electrode, whereas for partial discharges a stainless steel needle was employed. Complementary investigations on the chemical composition within the solid counter electrode material by secondary neutral mass spectrometry (SNMS) were also carried out. Under sparking conditions, the electrode material plays an important role in the decomposition rates of the gas-phase, but no relevant material dependence could be observed under partial discharge conditions.

Propagation and post-acceleration of a pseudospark-sourced electron beam

Abstract: Propagation and post-acceleration of a pseudospark-sourced electron beam from a three-gap pseudospark discharge chamber were studied in recent experiments. The pseudospark produced an electron beam of two phases, an initial 22 kV, 50 A hollow cathode phase beam of brightness 109−10 Am−2 rad−2 followed by a 200 V, 200 A conductive phase (CP) beam of brightness 1011−12 Am−2 rad−2. The aim of these experiments was to post accelerate the lower-voltage, higher-current CP beam using an acceleration unit driven by a 40 kV, 125 ns voltage pulse produced by a cable Blumlein. The experiments were realized by attaching an acceleration unit to the downstream side of the anode of the discharge chamber. Both the pseudospark discharge and the cable Blumlein were triggered to ensure time correlation between initiation of the pseudospark discharge and post-acceleration of the beam.

Generation of Radicals using Discharge inside Bubbles in Water for Water Treatment

Abstract: A new method for a water treatment utilizing radicals produced by a discharge inside bubbles in water is proposed. Radicals with short lifetime (atomic oxygen and OH radical) are used effectively for the water purification because those are generated by discharge inside bubbles in water. OH radical production was confirmed by a light emission of the discharge using the spectroscopic technique. Dissolved ozone concentration of about 0.3 mg/l was obtained when oxygen was used as a bubbling gas. Decolorization process of indigo solution by a discharge inside bubbles in water was investigated.

Negative ion generator

Abstract: A negative ion generator, which can suppress positive ion generation, permits ready control of a quantity of generated negative ions and permits a size and thickness reduction. The negative ion generator is of an electron emission type in which, for negative ion generation, electrons are emitted into the air by impressing a negative high voltage on a stylus electric discharge electrode. A piezoelectric transformer is used for amplifying a non-rectified drive voltage from a transformer drive circuit. As a result of rectification of the AC high voltage from the piezoelectric transformer, a negative high voltage is obtained, which is impressed on the stylus electric discharge electrode for electron emission therefrom, thereby generating negative ions in the air.

The DC glow discharge at atmospheric pressure

Abstract: The transition of a negative corona discharge into a glow discharge at atmospheric pressure is investigated. The volt-ampere characteristics of a pin-to-plate discharge configuration reveal the existence of three discharge regimes: corona, glow, and spark. The discharge luminosity is indicative of the differences in the electrical field distribution in the different regimes.

Exhaust emission control device for internal combustion engine

Abstract: PROBLEM TO BE SOLVED: To perform efficient exhaust emission control by the generated amount of electric discharge smaller than in the past. SOLUTION: A plurality of insulating substrates 15 are arranged in parallel in an emission control housing 14, a flow path 16 for exhaust gas is formed between each insulating substrate 15, also a plurality of electric discharge electrodes 17 are respectively embedded in each insulating substrate 15, and the exhaust gas is purified by generating a discharge in each flow path 16. For changing a discharge generated amount, according to the distribution of a flow amount of exhaust gas in the emission control housing 14, an electric discharge electrode 17a positioned in a central part of the emission control housing 14 is formed in the widest lateral width, to obtain the largest discharge area, from here the discharge electrode 17, as it goes toward a peripheral part (lateral direction and vertical direction), is formed in small lateral width, to obtain a small electric discharge area. In this way, the distribution of the generated amount of electric discharge in the emission control housing 14 generates the largest generated amount of electric discharge in the central part of the emission control housing 14 having a large flow rate of exhaust gas, the generated amount of electric discharge, in accordance with going toward the peripheral part of a small flow rate of exhaust gas, is decreased.

Discharge lamp igniter device and projector device

Abstract: A discharge lamp igniter for igniting a discharge lamp (1) comprises an igniter (2) serving as a starting means for igniting the discharge lamp (1) by applying a starting voltage to the discharge lamp (1) at starting the discharge lamp (1), a voltage determining circuit (3) for determining the voltage of the discharge lamp (1), and a current control circuit part (5) for controlling the current supplied to the discharge lamp (1) according to the result of the determination of the voltage determining circuit (3). After the ignition, the current control circuit part (5) starts the control of the current supplied to the discharge lamp (1) according to the result of the determination by the voltage determining circuit (3) and continuously varies the current supplied to the discharge lamp (1) at a predetermined rate of increase. In such a way, an inexpensive discharge lamp igniting device excellent in reliability and leading to a prolonged life of the discharge lamp (1) is provided.

Chemical kinetics with electrical and gas dynamics modelization for NOx removal in an air corona discharge

Abstract: A non-stationary reactive gas dynamics model in a mono-dimensional geometry, including radial mass diffusion, gas temperature variation and chemical kinetics, is developed in this paper. The aim is to analyse the spatio-temporal evolution of the main neutral species involved in a corona discharge used for NO pollution control in polluted air at atmospheric pressure and ambient temperature. The present reactive gas dynamics model takes into account 16 neutral chemical species (including certain metastable species) reacting following 110 selected chemical reactions. The initial concentration of each neutral species is obtained from a 1.5D electrical discharge model. The gas temperature variations are due to direct Joule heating during the discharge phase, and also result from the delayed heating due to the relaxation of the vibrational energy into a random thermal energy during the post-discharge phase. The simulation conditions are those of an existing experimental setup (anode voltage of 10 kV in the case of a point to plane geometry with an interelectrode distance of 10 mm). The obtained results show that the diffusion phenomena and the gas temperature rise affect quite well the gas reactivity and the neutral species evolution. This allows us to better understand the different reaction processes and transport phenomena affecting the NO concentration magnitude inside the discharge channel.

Features of sterilization using low-pressure DC-discharge hydrogen-peroxide plasma

Abstract: This investigation studies the theoretical and practical features of sterilization using glow discharge plasma in hydrogen-peroxide vapor. It is determined that in such a system, most sterilization is performed by the active species formed in the plasma rather than by ultraviolet radiation (as is the case in air or oxygen discharges). This study shows that sterilization by discharge plasma in hydrogen-peroxide vapor is more efficient than sterilization by other gas discharges: sterilization time is two to three times shorter in open surfaces and ten times shorter in packed articles. This study's calculations indicate that this enhanced efficiency might be due to fact that concentrations of the main biologically active particles, such as atomic oxygen and oxygen molecules excited to lower metastable states, reach values of /spl sim/10/sup 14/-10/sup 15/ cm/sup -3/, which is two to three orders of magnitude higher than that in oxygen plasma at the same parameters of the discharge.

Discharge source with gas curtain for protecting optics from particles

Abstract: A gas curtain device is employed to deflect debris that is generated by an extreme ultraviolet and soft x-ray radiation discharge source such as an electric discharge plasma source The gas curtain device projects a stream of gas over the path of the radiation to deflect debris particles into a direction that is different from that of the path of the radiation The gas curtain can be employed to prevent debris accumulation on the optics used in photolithography Preferably, the gas curtain flows at supersonic speeds

Surface modification of Al-Zn-Mg alloy by combined electrical discharge machining with ball burnish machining

Abstract: The study investigated the feasibility of modifying the surface of Al–Zn–Mg alloy by a combined process of electric discharge machining (EDM) with ball burnish machining (BBM). A novel process that integrates EDM and BBM is also developed to conduct experiments on an electric discharge machine. Machining parameters of the combined process, including machining polarity, peak current, power supply voltage, and the protruding of ZrO2, are chosen to determine their effects on material removal rate, surface roughness and the improvement ratio of surface roughness. In addition, the extent to which the combined process affects surface modification is also evaluated by microhardness and corrosion resistance tests. Experimental results indicate that the combined process of EDM with BBM can effectively improve the surface roughness to obtain a fine-finishing and flat surface. The micropores and cracks caused from EDM are eliminated during the process as well. Furthermore, such a process can reinforce and increase the corrosion resistance of the machined surface after machining.

Observation of transformation of chemical elements during electric discharge

Abstract: Results of experimental studies of electric explosion, in water, of foils made of extremely pure materials are presented. New chemical ele- ments detected both by spectroscopic measurements during the electric dis- charge and by a mass-spectrometer analysis of sediments after the discharge have been found to appear. A "strange" radiation associated with the trans- formation of chemical elements has been registered. A hypothesis has been put forward that particles of the "strange" radiation have magnetic charge.

Experimental study of HPS lamp ignition by using LC network resonance

Abstract: This paper presents a study of the HPS lamp behavior before ignition is achieved. The voltage generated by a LC network is applied to the lamp leads using the soft-start-up method. Modifications of the off state lamp equivalent resistance are observed when applying different ignition sequences. From the experiments, a breakdown characteristic is defined.

Gaseous electrical discharge characteristics in air and nitrogen at cryogenic temperature

Abstract: In designing superconducting electrical power apparatus, the knowledge of cryogenic gas and liquid insulation characteristics is essential. The authors have studied the discharge characteristics of relatively long-gap configurations in air and nitrogen at a cryogenic temperature. A sphere-to-sphere electrode with a gap length of 20 to 150 mm is used for measurements in uniform electric field. The breakdown voltage characteristics basically obey Paschen's law at cryogenic temperature for 50 Hz, AC, DC and lightning impulse voltage applications. A rod-to-plane electrode with a gap length of 20 to 330 mm is used for measurements in nonuniform electric field. In air at cryogenic temperature and nitrogen gas at both room and cryogenic temperature, streamer-like corona discharge appears near the tip of the rod electrode before the breakdown, and the breakdown voltage increases linearly with gap length. In air at room temperature thin film-like corona discharge, however, appears near the tip of the rod electrode before breakdown, and the breakdown voltage becomes higher than the other case. In order to examine the variation of corona discharge characteristics, some additional experiments are conducted. As a result, it becomes clear that thin film-like glow corona discharge appears when electronegative gas is contained and sufficient electrons are supplied from the cathode.

Experimental study of the influence of nanoparticle generation on the electrical characteristics of argon–silane capacitive radio-frequency plasmas

Abstract: The nonintrusive detection of particle contamination problems is of great interest to plasma processing in the manufacture of semiconductors. We have studied the influence of particle generation in argon–silane capacitive plasmas on the electrical discharge properties which can be nonintrusively measured with a current–voltage sensor. The Fourier components of the rf current and voltage and the respective phase angles between these signals have been studied up to the fifth harmonic of the 13.56 MHz rf power. We show that in particular higher harmonics are much more sensitive to the appearance of particles than the signals at the fundamental frequency or the second harmonic. It appears that the observation of higher harmonics is capable of providing early indication of particle growth in capacitive rf discharges.

A Detailed Two-Dimensional Numerical Study of Spark Ignition Including Ionization

Abstract: In this work, the spark–ignition (SI) of a methane/air mixture contained in a constant–volume chamber is investigated by numerical simulations. A cylinder–shaped vessel filled with a methane/air mixture containing two electrodes is used as simulation model. The impact of an electrical discharge at the electrodes on the surrounding gas is simulated, with detailed treatment of the ignition process involvig chemical kinetics, transport phenomena in the gas– phase and electrodynamical modeling of the interaction between spark and fuel/air mixture. For the calculations, a 2D–code to simulate the early stages of flame development, shortly after the breakdown discharge, has been developed. Computational results are shown for ignition of a methane air–mixture.

Fluorescent lamp, fluorescent lamp unit, liquid crystal display device, and method of emitting light

Abstract: A liquid crystal display device has a fluorescent lamp and a driving circuit as a back light. A closed container, a discharge gas sealed in the closed container, first discharge electrodes, and second discharge electrodes are included in the fluorescent lamp. The driving circuit repeats a first step of causing electric discharge in first discharge areas by applying a voltage having a negative polarity to the first discharge electrodes and a voltage having a positive polarity to the second discharge electrodes, and a second step of causing electric discharge in second discharge areas which are different from the first discharge areas by applying a voltage having a positive polarity to the first discharge electrodes and a voltage having a negative polarity to the second discharge electrodes.

Plasma display panel drive method

Abstract: In the reset step for initializing an amount of wall charge in each of the plurality of discharge cells that define each of the picture elements in a plasma display panel, the number of reset discharges that are caused to occur in the discharge cells that handle the emission of light of at least one color within the picture element is greater than the number of reset discharges that are caused to occur in the discharge cells that handle the emission of light of the other color(s). The plasma display panel drive method provides a stable electrical discharge effect while increasing contrast.